1. Field of the Invention
This invention relates to a bonded assembly of zirconia ceramic to platinum or other noble metal that employs an alignment ferrule comprised of titanium or an alloy of titanium. The assembly is suitable for implantation in living tissue.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
This invention is concerned with achieving a hermetic bond for an implantable medical device, where the bond is between a ceramic, preferably partially stabilized zirconia, and a noble metal, preferably platinum. A titanium or titanium alloy alignment ferrule provides a transition to allow a noble metal ring to be brazed to the alignment ferrule which is in turn welded to a noble metal eyelet or end cap. It is known that noble metal can be bonded by brazing to ceramic, U.S. Pat. No. 6,989,200. However, this has only been successful with butt joints and has not been previously demonstrated with step and lap joints, as required for certain applications such as where parts require self-centering.
It is desired that the end cap and eyelet, which are electrodes for contact with living tissue when implanted, can sustain high current density and have low impedance, as available only with noble metals, such as platinum, iridium, or their alloys.